Question 763232
Pipe1 takes 20 min to fill tank. So in 1 min it fills 1/20 of the tank.
Pipe2 takes 30 min to fill tank. So in 1 min it fills 1/30 of the tank.

Together, in 1 min, they fill (1/20 + 1/30) = 5/60 or 1/12 of the tank.
Hence to fill the tank, they would take {{{highlight(12)}}} minutes.


:)